The present invention relates to socket contacts which can be installed in a housing with a small spacing between the contacts for connection to a corresponding array of conductive pins that are insertable into the socket contacts to form an electrical connection.
Receptacle-type contacts are commonly manufactured by stamping a metal sheet to provide a carrier strip carrying a plurality of socket contact blanks. The contact blanks are subsequently bent into an appropriate shape, and the formed contacts are then inserted into a connector housing. Typically, the plurality of formed contacts on the carrier strip are inserted into the housing as a single unit ("gang insertion"), thereby simplifying and speeding the assembly process.
To permit multiple contacts to be inserted into the housing as a single unit, the contacts must be spaced from each other on the carrier strip by a distance which is an integral multiple of the pitch of the conductive pins which will mate with the contacts. It is preferred that the center-to-center spacing (e.g., pitch) of the formed contacts on the carrier strip equals the pitch of the conductive pins, so that only a single contact insertion step is required when installing a row of contacts in the connector housing. If the pitch of the contacts on the carrier strip is greater than the pitch of the conductive pins, multiple contact insertion steps are required to install a single row of contacts. For example, if the pitch of the contacts on the carrier strip is two times the pitch of the conductive pins, two insertion steps are necessary, with each insertion step installing one half (e.g., every other contact) of the row of contacts into the connector housing.
If the pitch of the finished contacts is to equal the pitch of the finished connector, then the width of each contact blank cannot be greater than the pitch of the finished contacts. Because there is a continuing trend toward miniaturization of connectors, the pitch of the connector pins and contacts (and thus the width of the contact blanks) is continually decreasing. As the pitch decreases, the formation of socket contacts using a stamping and bending procedure becomes increasingly difficult for dual beam contacts with oppositely disposed wipers. When the pitch of the connector becomes less than or equal to the maximum pin diameter times pi (e.g., circuit pitch .ltoreq.D.sub.max .pi.), a shortage of material occurs in the contact blank. That is, the amount of material required to form the contact blank is larger than the amount of available material on the carrier strip.
The material shortage problem is illustrated in FIG. 1A and FIG. 1B. FIG. 1A shows an example of a known socket contact 2 having a shank 4 and wipers 6 extending from shank 4. Wipers 6 are bent toward each other so as to capture a contact pin (not shown in FIG. 1A) inserted between wipers 6. It is desired to have the centerlines of wipers 6 align with the centerline of contact pin 8, so that uniform normal forces are applied to contact pin 8. FIG. 1B shows a cross section of socket contact 2 along line 1B--1B of FIG. 1A, with a contact pin 8 inserted into socket contact 2. As shown in FIG. 1B, contact pin 8 has a diameter of 0.018 inch, the socket contact 2 has a material width of 0.005 inch, wipers 6 have a half-width of 0.0055 inch, and a clearance of 0.001 inch is provided between shank 6 of contact pin 8 and socket contact 2. The centerline of socket contact 2 thus has a radius R of 0.0125 inch from the center of contact pin 8. The width of material needed to form socket contact 2 is the sum total of: 1) the centerline length of the curved portion of socket contact 2 (.pi.R =0.0393 inches ); 2) one half the width of each wiper 6 (0.0055 .times.2=0.0110 inches); and 3) the contact singulation width (0.0040 inches). The singulation width is the amount of material needed to account for separation of the individual contacts. Thus, to form shaped socket contact 2, a flat blank width of 0.0543 inch is required. If the pitch of the connector is 0.05 inch, for example, there will be a material shortage of 0.0043 inch, and the centerlines of wipers 6 of the formed socket contact 2 will not be positioned opposite each other on the centerline of contact pin 8.
When a material shortage occurs with the type of socket contact illustrated in FIG. 1A and FIG. 1B, there have been attempts to bring the wiper centerlines into alignment with the contact pin centerline by stretching the blanked material in the direction of arrows 9 during the shaping processes. However, this results in an unstable forming process and thus produces manufacturing difficulties. In addition, assembly issues also arise in attempting to control the contact location within the housing aperture to prevent the wiper edges from being the sole contact points which engage the pin.
There are some socket contacts stamped on connector pitch when the pitch is less than or equal to the maximum pin diameter times pi. For example, International Publication No. WO 9630969 nests the contact spring arms by staggering their position along the pin insertion axis. The resulting geometry provides a formed contact having one rigid contact beam and one compliant contact beam, with the contact points of the beams being offset along the pin insertion axis. The offset contact points cause unequal normal forces to be applied to the contact pin, which in turn results in undesirable pivoting of the contact on the pin. To ensure that both contact beams wipe the pin and to compensate for small variations in pin location, the contact body is stamped with a compliant waist having a reduced cross section. The reduced cross section of the contact causes current crowding in the area of the waist, and further encourages undesirable pivoting of the contact on the pin.
It is also known to deal with the material shortage problem by stamping and forming the socket contacts at slightly greater than connector pitch, and then pleating the carrier strip to move the formed contacts into an on pitch spacing. This method also has drawbacks, primarily that the pleated carrier strip is easily stretched. Thus, a complicated and expensive handling system is required for pleated carrier strips.
Because of the material shortage problem illustrated above, the majority of connector systems which have a circuit pitch which is less than or equal to the maximum pin diameter times pi, such as CompactFlash, PCMCIA and PCMIDE connectors, stamp the receptacle contacts on twice the circuit pitch. Prior art receptacle contacts of this type are exemplified in U.S. Pat. Nos. 4,678,278; 4,722,704; 4,874,338; 4,909,746; 4,720,277; and 5,597,324.
One type of receptacle socket contact is known as a dual-beam receptacle socket contact. One embodiment of such a contact is illustrated in FIG. 1A. A contact of this type includes a pair of resilient beams configured to grasp a conductive pin therebetween. The beams are disposed to contact opposite sides of a conductive pin inserted into the connector, and are formed to produce a contact force sufficiently low to allow easy pin insertion while at the same time providing the required contact force for long term ohmic contact upon insertion of the pin. The contact force must be sufficiently low to prevent undesirably high insertion force, plating wear, and bending of the pins during insertion while accommodating some variance in the positioning of individual pins, but high enough to ensure consistent electrical contact with the pin. Dual beam sockets are disclosed, for example, in U.S. Pat. Nos. 4,140,361; 4,591,230; 4,607,907; and 4,702,545.
What is needed is a socket contact which can be stamped from a flat metal sheet on connector pitch when pitch is less than or equal to pi times the maximum pin diameter, and which reduces or overcomes the disadvantages of the prior art socket contacts.